Ukraine tightens grip on rebels amid pressure for truce

Ukrainian President Petro Poroshenko was to face renewed European pressure on Wednesday to talk to pro-Russian rebels on a truce as Kiev tightened its grip around jittery rebel stronghold Donetsk.

French President Francois Hollande and German Chancellor Angela Merkel were expected to push the Western-backed leader on a ceasefire in three-way telephone talks but Kiev has until now shrugged off calls to halt an offensive that has reclaimed a string of key rebel towns.

Dressed in military fatigues Poroshenko on Tuesday made a triumphant visit to the vanquished rebel bastion of Slavyansk where government troops raised the national flag last week after pro-Moscow insurgents fled in the face of a fierce onslaught.

Poroshenko told reporters he would only speak "to the real masters of (the eastern region of) Donbass -- the steel workers and miners, people who hold the most power" in the conflict zone.

The resurgent leader promised to win back "very soon" the regional capitals of Donetsk and Lugansk but the rebels are digging in and have pledged to battle on.

Ukraine's military says it controls all routes in and out of the cities and a spokesman for Kiev's National Security and Defence Council warned a plan was in place that would give the rebels an "unpleasant surprise."

In Donetsk -- an industrial city of some 1 million people -- fears are mounting among the population that the mining hub will face clashes similar to the ones that gutted the city's airport in May.

Eyewitnesses told AFP that aircraft on Thursday carried out strikes on an abandoned mine where rebels are based in the western outskirts of the city.

Rebel military chief Igor Strelkov -- whom Kiev accuses of being a Moscow intelligence operative -- said fighters were working to reinforce the weak defences around Donetsk and bolster their numbers.

"We are taking urgent measures to prepare Donetsk for battle," Stelkov was reported as telling the insurgent's TV station Wednesday by Russia's state ITAR-TASS news agency.

Poroshenko -- who signed a historic political and trade deal with the EU last month -- tore up a 10-day ceasefire on July 1 because of uninterrupted rebel attacks that claimed the lives of more than 20 Ukrainian troops.

- Diplomatic tug-of-war -

Uneasy EU leaders are hoping that a new truce and a Kremlin promise not to meddle can take pressure off the bloc to adopt sweeping sanctions that could damage their own strong energy and financial bonds with Russia.

Russian President Vladimir Putin was to discuss the Ukraine crisis Wednesday with Italian Foreign Minister Federica Mogherini who is visiting Moscow after Rome took over the EU's rotating presidency.

The Kremlin has been unusually silent since the string of military advances by Kiev with analysts saying that Putin could be distancing himself from the rebels despite calls from hawks to send troops across the border.

Washington meanwhile has consistently backed the stepped-up campaign being waged by Ukrainian troops and irregular forces since Poroshenko's promise after his election in May to quickly quash an uprising that has cost nearly 500 lives and inflamed East-West ties.

The United States views Ukraine's territorial integrity as vital to European security and important to halting Putin's seeming ambition to resurrect a tsarist or post-Soviet empire.

Poroshenko on Tuesday dismissed the man who had headed Kiev's self-proclaimed "anti-terrorist operation" since its launch on April 13 and replaced him with Vasyl Grytsak -- a career security service officer.

The reshuffle was one of several in the Ukrainian Security Service (SBU) and appeared to represent an attempt by Poroshenko to place trusted associates in top positions rather than any change in tactic in the campaign.